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CHAPTER SIX
Gas flooding compared with
huff-n-puff gas injection
Abstract
This chapter is to discuss gas flooding in shale and tight oil reservoirs and to compare
the gas flooding with the corresponding huff-n-puff gas injection. A few field projects
are presented. The feasibility of gas flooding is briefly cited from a reference.
Keywords: Feasibility; Field projects; Gas flooding; Huff-n-puff gas injection.
6.1 Introduction
Gas flooding is much more commonly used than huff-n-puff gas
injection in conventional reservoirs. However, in shale or tight reservoirs,
because of ultra-low permeability and the resulting significant pressure
drop in the matrix, it is very difficult for the gas to drive oil from an injector
to a producer. If a shale or tight reservoir has natural fracture networks or the
hydraulic fractures connect an injector and a producer, gas will easily break
through, resulting in very low sweep efficiency (Sheng and Chen, 2014). To
avoid these problems, huff-n-puff gas injection is preferred. Regardless, gas
flooding is still an important EOR method, particularly in tight reservoirs
where the reservoir permeability is not as low as shale reservoirs. This chap-
ter discusses gas flooding in shale and tight formations, and to compare with
huff-n-puff gas injection. A few field projects are presented.
6.2 Research results on gas flooding
Yu and Sheng (2016a) used Eagle Ford outcrop cores to conduct ni-
trogen flooding tests. The core dimensions were 1.5 inches in diameter and
2 inches in length. The porosity was about 5% and the permeability was
about 70 nD estimated using AutoLab 1000 developed by NER Inc.,
USA (however, the estimated gas permeability was 0.5 nD Core GF_6
and 5 nD for Core GF_7 if the steady-state Darcy equation is used and
the data presented in the paper are used, indicating that different
Enhanced Oil Recovery in Shale and Tight Reservoirs © 2020 James Sheng.
ISBN: 978-0-12-815905-7 Published by Elsevier Inc.
https://doi.org/10.1016/B978-0-12-815905-7.00006-2 All rights reserved. 133 j
